PROJECT SUMMARY/ABSTRACT The purpose of this F32 application is to provide support for Dr. Vienna Brunt, a promising new postdoctoral fellow in the laboratory of Dr. Douglas Seals, to conduct research and training that will prepare her to become an independent investigator in the field of translational cardiovascular aging and prevention of cardiovascular diseases (CVD). As part of her proposed training plan, she will learn a variety of new technical, conceptual, and professional skills, including gaining experience in a new area of experimental research for her: preclinical research in mice. Her proposed research project seeks to investigate the role of trimethylamine N-oxide (TMAO) in mediating declines in vascular endothelial function with advancing age, a key pathophysiological step in the development of CVD. TMAO is a gut-derived metabolite produced via breakdown of dietary choline and L-carnitine by gut bacteria, whose prevalence in the gut increases with advancing age and with disease progression. Elevated TMAO has been linked to several common diseases, including atherosclerosis; however, whether it mediates the declines in endothelial function that lead to clinically manifest CVD is unknown. Guided by strong preliminary data, Dr. Brunt will investigate whether TMAO mediates endothelial dysfunction, and using innovative transgenic mouse models and ex vivo ?pharmaco-dissection? techniques, the underlying mechanisms will be investigated, specifically focusing on the role of superoxide-mediated oxidative stress (Aim 1). Furthermore, Dr. Brunt will test the ability of 3,3-dimethyl-1-butanol (DMB), a newly discovered inhibitor of TMAO production, to both prevent and treat age-associated endothelial dysfunction in middle-aged and older mice (Aim 2)?importantly, DMB, a compound found naturally in many foods, shows promise for translation to humans for reducing risk of CVD. Lastly, to provide translational insight, Dr. Brunt will take advantage of the large database available in the Seals Laboratory of plasma samples from previously phenotyped and characterized human subjects in order to determine whether associations between TMAO and endothelial dysfunction exist across aging in humans (Aim 3). Overall, the proposed research has the potential to address 2 important strategic research priorities of NHLBI: 1) investigate new pathobiological mechanisms important to the onset of CVD, and 2) identify a novel therapeutic strategy to prevent and treat age-associated endothelial dysfunction, thereby reducing risk of CVD. The sponsor, Dr. Seals, is an internationally recognized and NIH funded scientist with a strong history of successful mentoring in translational cardiovascular research. With his guidance, and the guidance of consulting mentors Dr. Anthony Donato and biostatistician Dr. Matthew McQueen, Dr. Brunt will be able to successfully complete the proposed research and training plan, preparing her to succeed as an extramurally-funded independent investigator in translational cardiovascular aging.